Mike Hansen

Donald Knuth would hate you. The interesting thing is that he interrupted his work on "The Art of Computer Programming" because he couldn't type set it to his esthetic standards, especially the mathematical formulas. So he developed TeX over many years, then completed the work on computer programming with TeX. TeX is now the de-facto standard word processor in the mathematical and many natural and engineering science faculties. From my experience at university, it's the mathematicians who are most picky about the beauty of their type setting. There's a difference between style (at least as I was using the term) and typesetting. I wasn't referring to style as the graphical look of the words, but rather the choice of words when options are available. My statement that formal mathematical writing is "pure content" was made because superfluous wording (the style which often just gets in the way) is often inappropriate for such writing. On a side-note, I'm the only ChemE student here at the U that uses LaTeX and LyX - Microsoft Word & Mathtype just don't do it anymore - so I am fairly familiar with Dr. Knuth and his terrific work with typesetting. Mike

Just wondering. Formal mathematical writing is pure content. Style only exists in the side-notes. It really puts things in perspective. You are correct, style definitely yields information about a person & his/her relationship to the ideas being discussed. If that's what you're after, then attention must be paid to style. If you're after a person's arguments & ideas, then simplification/clarification must be done as I've suggested above. It all depends on your goal. I just remember discussions before I figured out that I need to understand exactly what a person (myself included) is talking about before I can deal with it. So much time/effort wasted on political discussions where neither I nor my opponent knew what we were talking about. But we knew plenty of statements from pundits/politicians and had definite 'styles'... I guess a good rule of thumb would be to figure out if the person knows what they're talking about, and then pay significant attention to style. What do you think? Mike

Hi Sam, My thoughts: Style usually convolutes things, in that it turns arguments away from meanings & definitions and points them towards superficial labels. I always go after clarity in discussions. I restate what the person is saying in simpler terms, and ask them immediately if I'm bothered by their choice of words. Also, in a lot of cases a person who just copies arguments (in other words, a hack) from other people can't rephrase or clarify their statements. Thus asking for clarification in arguments has two helpful effects: (1) Allows for better discussion with people who are trying to find truth. (2) Lets you avoid meaningless conversations and wasted time with people who aren't trying to find truth. Mike P.S. Do you have any experience with formal mathematical writing?

Almost all christians will pervert the idea of judgement/criticism. "Oh, we can judge people harshly because we're really just trying to help them..." and the rest of that kind of crap. It's just not worth thinking about. There are too many issues, and attempting to generalize the issues & your arguments is simply not worth the work (however, I suppose if you're writing a book and such thoughts will further the achievement value and financial success of the book, then nevermind ). Best to write the rant thoroughly (see below) & quickly and get on to better things. How's the degree going? You start fall semester last week too? Mike EDIT/ADD: by thoroughly I mean to not leave anything in your head - buildup like that equals stress and, as Rand would say, would clog your motor.

Hi Dana. Where are you going to school? Do you prefer college football or NFL? As long as he doesn't have to run (er, attempt to run), Manning is great. But until the Colts lose Austin Collie (prick from BYU) I cannot cheer for them. Go Steelers & Bears... and any team with my fantasy players. Mike

I'm reading through my Heat Transfer textbook for this fall. It is a textbook written for juniors with experience in multivariable calculus, ordinary differential equations, and the first two years of physics & chemical engineering courses. But, when it needs to explain a concept that belongs to kinetic theory, it can't go into any detail, because kinetic theory is beyond our ability. All it can do is give a formula/result and explain it on a fairly superficial level. And in an introductory level course, the content of this heat transfer book is too complex. So all an intro course can do is give a formula/result and explain it on a fairly superficial level. The number of real-world situations you want to understand isn't the issue here. The fact is that the physics of real-world situations is a graduate-level topic. Simplified models persist throughout the entire undergraduate process (this heat transfer book is based entirely on them). Only in the last year do you get closer to reality. Then it's on-the-job learning. Not only is the physics difficult, but the math is as well. At the introductory level, assuming that students will know remedial calculus is hardly justifiable. Most will be taking their first calculus course at the same time. With the fact that most (~99%) undergraduates/freshmen don't have years of experience in physics and math, no introductory book will be able to cover the real-world applications which require such experience. In other words, if a book has to explain physics without referencing previous physics courses or any mathematics beyond high-school algebra... the possibility that it will approach a complex, real-world situation is zero. Even if the situation is looked at through the lens of a case study. The case studies I've done we're not geared towards teaching new concepts, but rather applying and combining the concepts we've already learned. It was great fun, combining everything we had learned to a large problem that felt like one from an industrial setting. But the problem I stated above remained: we still couldn't cover the advanced, real-world concepts that require the math & physics we didn't have. I suppose it is possible to write a survey-type book which can explain the real-world aspects of physics/engineering... but then it's my previous point that such a book would be HUGE.

Do you want a survey of engineering book or do you want to understand the physics of 'real-world' situations? You absolutely cannot get both at the same time. Unless you're satisfied with a description of airplane flight like "the lift force must overcome the weight of the aircraft" and a few very simple examples, a survey/introduction book is not what you want. From the earlier discussion, I had the impression that the simplicity of survey/intro books is what you are trying to get past. Do you honestly expect to find any complicated, real-world physics in such a book?

Well said. Feynman was terrific. An expert knowledge of science/engineering/math creates, in most people, a desire to share it with others who will appreciate it. An expert and a hard-working, enthusiastic student fit together perfectly. I would guess that an expert knowledge of anything would do that, but I only have experience with experts in science/engineering/math so I won't speak for other fields B) . Mike

Nope. We have general courses for the important subtopics (specialized courses exist in grad school). I've mentioned my "Statics & Strengths of Materials" course several times now... well the U of U is unique in combining those courses into one semester. Most universities have Statics as one semester and Strengths as the next. A general book covering all of engineering in any level of detail would be huge. We're talking tens, if not hundreds, of thousands of pages. Same for all of mechanical eng. or all of chemical eng. or all of any other discipline. The reason for the specialization: the best engineering students will spend four to seven years essentially cramming (but still retaining most of the information, not just losing it after each semester), only to get to a 'real-world' example and have to learn more. And if they want to become specialists (as I do), good god there is a lot more to learn (without losing the other info). Helpful words from a professor I liked: "The only way to learn mechanics is to do mechanics" Mike

Sounds like trusses would interest you quite a bit. This website should help: http://emweb.unl.edu/negahban/em223/note12/note12.htm When I took my Statics and Strengths of Materials course, we did a few "real" problems, but things can get really complicated really quickly. Also sounds like Shear & Bending Moment Diagrams would intrigue you. This website is very dense and not easy but should be interesting: http://ocw.mit.edu/courses/materials-science-and-engineering/3-11-mechanics-of-materials-fall-1999/modules/statics.pdf I looked up "Structural Analysis" on Amazon.com. There's a book by R.C. Hibbeler under that title. I've had two of his textbooks in the past and he is terrific. (Maybe go for an older edition, though, since the newer ones are fairly expensive) Mike

Change is the act of going from one state to another. It's always occurring and there is plenty to be afraid of (also plenty to be happy about). This thread is appearing more and more like intellectual masturbation. I'll echo David Lee's post: how can these ideas be useful?

I am a junior in chemical engineering, at the University of Utah. Those times when the book says "it can be shown", give google a try. A lot of science/math/engineering professors post their notes online (usually you'll see them as the first search results), and I've found wikipedia to be fairly useful and very accurate with regards to scientific matters. Wikipedia is particularly nice in that you can often get those derivations that a lot of textbooks lack. By the time you get to fluid mechanics, I guarantee that you will begin to despise the monstrosity that is the English unit system. In statics, things aren't too bad, but I have a feeling you'll start working in metrics and then converting to English. It's not just the fact that it is base-10. It's the conversion factors required in English units. Pound-force versus pound-mass is only the beginning! Mike

I'm not sure what you mean by limited and infinite. Regardless:

It may be a horizontal structure, but the support force it provides (through its supports i.e. the nails holding it in the wall) is vertical. Just do a force diagram on the backpack with encyclopedias system: Let T represent the tension in the ropes, and W be the weight of the pack. The resulting force balance is: T = T (x-component) W = 0 (y-component) The only way this system may be balanced is if W = 0. You may have been able to move the backpack above the horizontal for a moment, but I guarantee you will not be able to suspend it there. However, if we hang the backpack on a bar that is fixed in the wall, then we should consider not the backpack, but the backpack AND the bar. And when we do that, we move from a point mass to a rigid body. (It's not really important in this case, but a rigid body is different because it can rotate, so we obtain one more equilibrium condition: the sum of the torques equals zero). If we write a force balance for the backpack and bar system, and let Rx and Ry be the reaction forces of the wall, we get: Rx = 0 Ry = W So while the bar is horizontal, it supplies a vertical force (well, really the wall supplies the vertical force, the bar just translates it). You're thought about the non-uniform translation of shear stress is correct, but it doesn't matter here. Would the distribution of stress matter at all if there was no vertical force countering the weight? If Ry in the equation above is zero, the system cannot hold a weight and be at equilibrium, no matter how the stress varies. The statements that "a purely horizontal force can't do anything to counter a vertical force" and "the force required to suspend the object...will asymptote to infinity as you get closer to the horizontal. It is literally impossible to suspend the object if there is no angle with the horizontal" are really the exact same thing. And on the topic of seeing the physics in action, it's definitely very important! I had a terrific physics professor who always had about ten 'toys' out for every lecture. I had an awful physics teacher in high school, though. Maybe one or two demonstrations for a whole year. Pretty hard to learn physics without a large number of guided observations. Mike

Well when you've got a force at a five degree angle, only nine percent of the force is in the y-direction. And a purely horizontal force can't do anything to counter a vertical force. Here's a thought experiment, or if you really want to be convinced, give it a try for real: Take a light weight and attach two strings to it. One outwards to the right and the other to the left. Now suspend the weight by holding the ends of the strings. If the strings are vertical, your hands only have to supply a force equal to the weight of the object. Now place your hands at approx. forty-five degree angles from the horizontal (or vertical I guess!). It's quite a bit harder to hold the weight up, because only half of your supplied force is actually acting vertically. So you literally need twice the force to suspend the object. Now move your hands such that the strings get closer and closer to horizontal. Because you're essentially dealing with one quarter of the unit circle when moving your hands, you will feel a "parabolic" change in the force required to suspend the object. It's not really parabolic, though, because it will asymptote to infinity as you get closer to the horizontal. It is literally impossible to suspend the object if there is no angle with the horizontal. (For extremely light weights we can get the string to be apparently straight, but our eyes can only detect angles above a certain threshold. If you want to try this for real, use a weight of a pound or more.) Mike

No mistake in the force equations. Your force balance for point A is correct. I've tried to figure out a few things to write about the quoted material above, but I'm a little confused about your thought that the force equations break down. Please elaborate. Mike

Okay. I'll bite. If we define C to be the force on the cable, S to be the force on the strut, and W to be the weight of the heavy weight, we proceed with a force balance to get: x-component: Ccos(30) = Scos(45) y-component: Csin(30) + Ssin(45) = W The 'tricky' part: the x-component of the balance gives us an equation for two variables (S and C) that we probably think we already know (from their given maximum values). Plugging in the maximum values, the x-component shows that S = 1225 lbs, instead of its maximum of 2000 lbs. (the logic here is that 2000*cos(45) is greater than 1000*cos(30), which means that, for the equality to be satisfied, C must increase (impossible. already at maximum) or S must become the value that gives the equality). Then plugging in the value of C = 1000 lbs, S = 1225 lbs, we get the maximum weight W = 1366 lbs. Mike

This is when a definition of "god" is necessary. But if you make your definition such that the god you are referring to (a limited god or whatever you want to call it) has only a few (if any) characteristics in common with most of the religiously-created gods, then you probably ought to use a different word. Plus, using a different word would remove all that mental baggage associated with "god". Mike

Oh jeez I did about eight thousand variants of this problem in my Statics & Strengths of Materials course. As soon as I saw the words "strut", "heavy weight", and "cable", I knew exactly what was coming. Yep... If we can't dazzle them with brilliance... Mike

I think you've got it! Then again the Utes are in the Pac-12 this year so I wouldn't be at too much of a loss if there was no NFL Season. However, I can't imagine life without fantasy football! If you're referring to the CFL... I just don't know what to say . If you are referring to Soccer... well it's my opinion that no game should be allowed to end in a scoreless tie! Mike

Thank you. Seriously, IT IS A RANT. Not a set of well thought-out, serious, generalized statements with the goal of promoting a profound idea... it is a rant, purely with the goal of letting loose some steam in what is likely to be a supportive environment. Now, if I came in here and presented a formal case for the ideas I said above, then you can and should rip right into it, for such ideas are formally nonsense. Of course I don't feel this way about ALL religious people (nor did I bother defining what makes a person religious - that should give a clue as to my state of mind at the time. Really though, what the hell does "religious people" even mean? True believers? Church-goers? What?). And of course I don't think that people become "douchebag-safe" by becoming atheists (not sure how I prompted that one but whatever). To Xray: I agree (today!) that the statement isn't really horrific/hilarious. I think ironic is a better term. Reinforcing a belief system right before acting against it... yep, ironic is definitely the correct term. Also, thanks for the clarification on Dawkins' idea. Mike

Hi everybody, Just a little rant tonight. I am getting pretty sick of religious people, mainly because not a single one of them actually lives by the code they 'attack' us with... I was going to try to make that line sound cool, but it's a rant. Screw it. Anyways, today I was in a conversation with a mormon, who is usually not too bad, and I was the recipient of a statement that is both hilarious and horrific. Essentially, it was "you need to stop swearing around me because I'm really losing respect for you." HAH! Recipe for this type of awful statement: (1) Utilize a set of moral standards (which you apparently live by) in attacking an action. (2) Immediately act in a way (judging other people) described as evil by the same standards. Ugh. I've been thinking a lot about the claim that religion is child abuse (I think it was Richard Dawkins that I heard that from). I completely agree. What a way to subtly ruin a person's childhood, and if successful, their adult life too! ... anybody have a method for forgetting that we're surrounded by such people?

You are sharing that hammer over there now aren't you?

I'll play. I've played chess since I can remember. I've played chess well since middle school. Read quite a few books and a lot of practice ended up giving me a third-place finish in the Utah state high school tourney. Haven't played much since then, but I'll give it a go. Mike

Well said. Caveat Emptor!